Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 196,782,000		$ 39,100,000		$ 288,132,000	$ 118,876,000
Gross losses on investment securities	(8,920,000)		(18,872,000)		(32,271,000)	(65,000,000)
Gains on investment securities, net	187,862,000		20,228,000		255,861,000	53,876,000
Gains attributable to noncontrolling interests, including carried interest	151,360,000		12,776,000		204,723,000	34,616,000
Fair value accounting | Other Securities [Member]
Gain (Loss) on Investments [Line Items]
UnrealizedGainsRelatedToSingleInvestment	139,000,000
Gross gains on investment securities	143,840,000		0		143,840,000	0
Gross losses on investment securities	(75,000)		0		(75,000)	0
Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Recognized other-than-temporary impairment (OTTI) losses	400,000				1,200,000
Number of other-than-temporary impaired investments	12				37
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	317,000	[1]	20,000	[1]	3,167,000	5,363,000
Gross losses on investment securities	(98,000)	[1]	(121,000)	[1]	(2,218,000)	(1,771,000)
Marketable Securities | Fair value accounting
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0		255,000		4,345,000	3,874,000
Gross losses on investment securities	0		(553,000)		(2,534,000)	(1,307,000)
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	35,826,000		28,639,000		107,546,000	88,037,000
Gross losses on investment securities	(1,575,000)		(16,557,000)		(17,020,000)	(49,090,000)
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	5,180,000		2,515,000		8,020,000	5,848,000
Gross losses on investment securities	(587,000)		(125,000)		(2,241,000)	(10,007,000)
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0		0		0	21,000
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	6,569,000		5,571,000		14,038,000	12,382,000
Gross losses on investment securities	(1,944,000)		(1,091,000)		(2,421,000)	(1,794,000)
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	5,016,000		694,000		6,806,000	1,639,000
Gross losses on investment securities	(689,000)		(423,000)		(1,462,000)	(963,000)
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	34,000		1,406,000		370,000	1,712,000
Gross losses on investment securities	$ (3,952,000)		$ (2,000)		$ (4,300,000)	$ (68,000)

[1] Includes realized gains on sales of available-for-sale securities that are recognized in the income statement. Unrealized gains on available-for-sale securities are recognized in other comprehensive income and not shown in the table above. The cost basis of available-for-sale securities sold is determined on a specific identification basis.